Carbon deposition on borated alumina supported nano-sized Ni catalysts for dry reforming of CH 4

Abstract

Borated alumina supported 5wt% Ni catalysts with B 2O 3 loading varying from 0wt%, 1wt%, 5wt% to 10wt% were prepared and characterized by XRD, H 2-TPR, CO 2-TPD, NH 3-TPD, in situ DRIFTS study, and evaluated for dry reforming of methane. The addition of B 2O 3 influences the activity and stability of the catalysts significantly. Ni particle size increases from 5.8 to 9.1nm with increasing the B 2O 3 loading from 0 to 10wt%. In the kinetic control temperature region (700°C) there is no linear relationship between the Ni particle size and the catalyst activity/stability. The formation of strong Lewis acid sites causes severe carbon deposition on 1wt% and 10wt% B 2O 3 loaded Ni catalysts, hence decreasing catalytic activity and stability. The formation of weak Lewis acid sites and O-H groups on 5wt% B 2O 3 promoted Ni catalyst is found to significantly facilitate carbon removal and improve the stability of the catalysts. The reaction mechanism of dry reforming of methane over borated-alumina supported Ni catalysts is proposed, especially the promotional effect of OH groups on the suppression of carbon formation being emphasized. © 2012 Elsevier Ltd.